Decorative and durable coating having a homogeneous hue, methods for their preparation, and articles coated therewith

ABSTRACT

Disclosed are powder coating compositions suitable for producing a decorative and durable coating having a homogeneous hue, articles comprising a decorative and durable coating having a homogeneous hue deposited thereon, methods for preparing a decorative and durable coating having a homogeneous hue, kits capable of producing a decorative and durable coating having a homogeneous hue, and methods for color matching using powder coating compositions.

FIELD OF THE INVENTION

The present invention relates to powder coating compositions suitablefor producing a decorative and durable coating having a homogeneous hue,articles comprising a decorative and durable coating having ahomogeneous hue deposited thereon, methods for preparing a decorativeand durable coating having a homogeneous hue, and kits capable ofproducing a decorative and durable coating having a homogeneous hue.

BACKGROUND INFORMATION

Powder coatings compositions for use in coating various types ofsubstrates are often desired. Such coating compositions can greatlyreduce, or even eliminate, the use of organic solvents that are oftenused in liquid coating compositions. When a powder coating compositionis cured by heating, little if any volatile material is driven into thesurrounding environment. This is a significant advantage over liquidcoating compositions in which organic solvent is volatized into thesurrounding atmosphere when the coating composition is cured by heating.

Powder coating compositions are typically produced by a complex processthat includes dry blending various coating components, such as colorpigments, film-forming resins, curing agents, and other additives, suchas flow control agents and charge control agents, subjecting theresulting blend to heating, melting and kneading by the use of anextruder or the like, and then subjecting the resulting extrudate tocooling, grinding and classification (referred to herein as the“Extrusion Process”). Thus, the Extrusion Process requires many steps.

One disadvantage to the use of powder coating compositions has beenthat, to obtain various coatings of different hues, the production of aseparate powder coating composition for each desired hue has beenrequired. When liquid coating compositions of different hues are mixed,it is possible to obtain a coating having a homogeneous hue that isdifferent from the hue of each mixed liquid coating composition. On theother hand, when typical powder coating compositions of different huesare dry-blended and the resultant blend applied to a substrate, theresult is that each hue can be generally distinguished by visualexamination with the naked eye, resulting in a “salt and pepper” effect.Thus, it has previously been difficult, if not impossible, to achieve acoating of a desired hue from a dry blend of two or more powder coatingcompositions of different hues.

As a result, it would also be desirable to provide powder coatingcompositions suitable for producing a decorative and durable coatinghaving a selected homogeneous hue from a dry blend of two or more powdercoating compositions each having a different hue.

SUMMARY OF THE INVENTION

In certain respects, the present invention is directed to powder coatingcompositions suitable for producing a decorative and durable coating.These coating compositions comprise a mixture of a first powder coatingcomposition having a first hue and a second powder coating compositionhaving a second hue different from the first hue. Moreover, the firstpowder coating composition and/or the second powder coating compositioncomprises polymer-enclosed color-imparting particles. The powder coatingcompositions of the present invention, upon direct application to atleast a portion of a substrate and cure, produce a decorative anddurable coating having a homogeneous hue different from the first hueand the second hue.

In other respects, the present invention is directed to articlescomprising a decorative and durable coating having a homogeneous huedeposited thereon. The decorative and durable coating is depositeddirectly from a powder coating composition comprising a mixture of afirst powder coating composition having a first hue and a second powdercoating composition having a second hue different from the first hue,wherein the first powder coating composition and/or the second powdercoating composition comprises polymer-enclosed color-impartingparticles. In the articles of the present invention, the homogeneous hueis different than the first hue and the second hue.

In yet other respects, the present invention is directed to methods forpreparing a decorative and durable coating having a homogeneous hue.These methods comprise: (a) providing a first powder coating compositionhaving a first hue, (b) providing a second powder coating compositionhaving a second hue different than the first hue, (c) mixing the firstpowder coating composition and the second powder coating composition,and (d) directly applying the mixture to at least a portion of asubstrate. In these methods, the first powder coating composition and/orthe second powder coating composition comprises polymer-enclosedcolor-imparting particles.

In still other respects, the present invention is directed to kitscomprising: (a) a first container comprising a powder coatingcomposition having a first hue, and (b) a second container comprising apowder coating composition having a second hue different from the firsthue. In the kits of the present invention, the first container and/orthe second container comprises a powder coating composition comprisingpolymer-enclosed color-imparting particles, and upon mixture of thecontents of the first container with the contents of the secondcontainer, a powder coating composition is formed that, upon directapplication to at least a portion of a substrate and cure, produces adecorative and durable coating having a homogeneous hue different fromthe first hue and the second hue.

The present invention is also directed to methods for color matchingusing powder coating compositions. These methods comprise: (a) providinga first powder coating composition having a first hue, (b) providing asecond powder coating composition having a second hue different than thefirst hue, (c) mixing the first powder coating composition and thesecond powder coating composition in a proportion that results in acoating having a desired homogeneous hue when the mixture is directlyapplied to at least a portion of a substrate and cured. In thesemethods, the first powder coating composition and/or the second powdercoating composition comprises polymer-enclosed color-impartingparticles.

DETAILED DESCRIPTION OF THE INVENTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

As previously mentioned, certain embodiments of the present inventionare directed to powder coating compositions suitable for producing adecorative and durable coating. As used herein, the term “powder coatingcomposition” refers to a composition suitable for producing a coating ona substrate, which is embodied in a solid particulate form, as opposedto liquid form. As used herein, the term “decorative and durablecoating” refers to a coating that is both decorative, i.e., it providesa desired appearance to the substrate, and durable, i.e., it does notsignificantly chip, peel, mar, or delaminate when subjected toenvironmental conditions, such as humidity and abrasion typicallyexperienced by a coating, such as coatings used on automotive and truckcomponents, such as bodies, door panels, cabs, trailer bodies; airplanecomponents, such as fuselage and wings; architectural components;consumer electronic equipment, such as computers and telephones; as wellas other articles. As a result, the “decorative and durable coatings” ofthe present invention are distinct from decorative coatings formed fromthe use of dyes or inks that are not durable.

The powder coating compositions of the present invention comprise amixture of a first powder coating composition having a first hue and asecond powder coating composition having a second hue different from thefirst hue. As used herein, the term “mixture” refers to a heterogeneousassociation of the first powder coating composition and the secondpowder coating composition, wherein the powder coating compositions arenot chemically combined and can be separated by mechanical means. Thefirst powder coating composition and the second powder coatingcomposition may be mixed by any method, such as, for example,dry-blending methods using high speed agitators, such as a Henchselmixer. In the present invention, as described herein, by producingpowder coating compositions of a limited number of colors (fundamentalcolors) and by examining, in advance, the relation between theproportions of these colored powder coating compositions and the hues ofthe coatings obtained therefrom, a powder coating composition ofvirtually any desired hue can be produced by appropriately selecting thecolored powder coating compositions and mixing them in the properproportion so as to give as desired homogeneous coating hue without theneed to subject the mixture to the Extrusion Process.

As previously indicated, the first powder coating composition and/or thesecond powder coating composition comprises polymer-enclosedcolor-imparting particles. In certain embodiments, the first powdercoating composition and the second powder coating composition bothcomprise polymer-enclosed color-imparting particles. As used herein, theterm “polymer-enclosed particles” refers to particles that are at leastpartially enclosed by, i.e., confined within, a polymer to an extentsufficient to separate particles from each other within the resultingcoating, such that significant agglomeration of the particles isprevented. It will be appreciated, of course, that a powder coatingcomposition comprising such “polymer-enclosed particles” may alsoinclude particles that are not polymer-enclosed particles. As usedherein, the term “color-imparting particle” refers to a particle thatsignificantly absorbs some wavelengths of visible light, that is,wavelengths ranging from 400 to 700 nm, more than it absorbs otherwavelengths in the visible region.

In certain embodiments, the particles that are enclosed by a polymercomprise nanoparticles. As used herein, the term “nanoparticles” refersto particles that have an average particle size of less than 1 micron.In certain embodiments, the nanoparticles used in the present inventionhave an average particle size of 300 nanometers or less, such as 200nanometers or less, or, in some cases, 100 nanometers or less. Thus, incertain embodiments, the powder coating compositions comprisecolor-imparting particles that are polymer-enclosed and, therefore, notsignificantly agglomerated.

For purposes of the present invention, average particle size can bemeasured according to known laser scattering techniques. For example,average particle size can be determined using a Horiba Model LA 900laser diffraction particle size instrument, which uses a helium-neonlaser with a wave length of 633 nm to measure the size of the particlesand assumes the particle has a spherical shape, i.e., the “particlesize” refers to the smallest sphere that will completely enclose theparticle. Average particle size can also be determined by visuallyexamining an electron micrograph of a transmission electron microscopy(“TEM”) image of a representative sample of the particles, measuring thediameter of the particles in the image, and calculating the averageprimary particle size of the measured particles based on magnificationof the TEM image. One of ordinary skill in the art will understand howto prepare such a TEM image and determine the primary particle sizebased on the magnification. The primary particle size of a particlerefers to the smallest diameter sphere that will completely enclose theparticle. As used herein, the term “primary particle size” refers to thesize of an individual particle.

The shape (or morphology) of the polymer-enclosed color-impartingparticles can vary. For example, generally spherical morphologies (suchas solid beads, microbeads, or hollow spheres), can be used, as well asparticles that are cubic, platy, or acicular (elongated or fibrous).Additionally, the particles can have an internal structure that ishollow, porous or void free, or a combination of any of the foregoing,e.g., a hollow center with porous or solid walls. For more informationon suitable particle characteristics see H. Katz et al. (Ed.), Handbookof Fillers and Plastics (1987) at pages 9-10.

Depending on the desired properties and characteristics of the resultantpowder coating composition (e.g., coating hardness, scratch resistance,stability, or color), mixtures of one or more polymer-enclosedcolor-imparting particles having different average particle sizes can beemployed.

The polymer-enclosed color-imparting particles, such as nanoparticles,can be formed from polymeric and/or non-polymeric inorganic materials,polymeric and/or non-polymeric organic materials, composite materials,as well as mixtures of any of the foregoing. As used herein, “formedfrom” denotes open, e.g., “comprising,” claim language. As such, it isintended that a composition or substance “formed from” a list of recitedcomponents be a composition comprising at least these recitedcomponents, and can further comprise other, non-recited components,during the composition's formation. Additionally, as used herein, theterm “polymer” is meant to encompass oligomers, and includes withoutlimitation both homopolymers and copolymers.

As used herein, the term “polymeric inorganic material” means apolymeric material having a backbone repeat unit based on an element orelements other than carbon. Moreover, as used herein, the term“polymeric organic materials” means synthetic polymeric materials,semi-synthetic polymeric materials and natural polymeric materials, allof which have a backbone repeat unit based on carbon.

The term “organic material,” as used herein, means carbon containingcompounds wherein the carbon is typically bonded to itself and tohydrogen, and often to other elements as well, and excludes binarycompounds such as the carbon oxides, the carbides, carbon disulfide,etc.; such ternary compounds as the metallic cyanides, metalliccarbonyls, phosgene, carbonyl sulfide, etc.; and carbon-containing ioniccompounds such as metallic carbonates, for example calcium carbonate andsodium carbonate.

As used herein, the term “inorganic material” means any material that isnot an organic material.

As used herein, the term “composite material” means a combination of twoor more differing materials. The particles formed from compositematerials generally have a hardness at their surface that is differentfrom the hardness of the internal portions of the particle beneath itssurface. More specifically, the surface of the particle can be modifiedin any manner well known in the art, including, but not limited to,chemically or physically changing its surface characteristics usingtechniques known in the art.

For example, a particle can be formed from a primary material that iscoated, clad or encapsulated with one or more secondary materials toform a composite particle that has a softer surface. In certainembodiments, particles formed from composite materials can be formedfrom a primary material that is coated, clad or encapsulated with adifferent form of the primary material. For more information onparticles useful in the present invention, see G. Wypych, Handbook ofFillers, 2nd Ed. (1999) at pages 15-202.

As aforementioned, the particles useful in the present invention caninclude any inorganic materials known in the art. Suitable particles canbe formed from ceramic materials, metallic materials, and mixtures ofany of the foregoing. Non-limiting examples of such ceramic materialscan comprise metal oxides, mixed metal oxides, metal nitrides, metalcarbides, metal sulfides, metal silicates, metal borides, metalcarbonates, and mixtures of any of the foregoing. A specific,non-limiting example of a metal nitride is boron nitride; a specific,non-limiting example of a metal oxide is zinc oxide; non-limitingexamples of suitable mixed metal oxides are aluminum silicates andmagnesium silicates; non-limiting examples of suitable metal sulfidesare molybdenum disulfide, tantalum disulfide, tungsten disulfide, andzinc sulfide; non-limiting examples of metal silicates are aluminumsilicates and magnesium silicates, such as vermiculite.

In certain embodiments of the present invention, the particles compriseinorganic materials selected from aluminum, barium, bismuth, boron,cadmium, calcium, cerium, cobalt, copper, iron, lanthanum, magnesium,manganese, molybdenum, nitrogen, oxygen, phosphorus, selenium, silicon,silver, sulfur, tin, titanium, tungsten, vanadium, yttrium, zinc, andzirconium, including oxides thereof, nitrides thereof, phosphidesthereof, phosphates thereof, selenides thereof, sulfides thereof,sulfates thereof, and mixtures thereof. Suitable non-limiting examplesof the foregoing inorganic particles are alumina, silica, titania,ceria, zirconia, bismuth oxide, magnesium oxide, iron oxide, aluminumsilicate, boron carbide, nitrogen doped titania, and cadmium selenide.

The particles can comprise, for example, a core of essentially a singleinorganic oxide, such as silica in colloidal, fumed, or amorphous form,alumina or colloidal alumina, titanium dioxide, iron oxide, cesiumoxide, yttrium oxide, colloidal yttria, zirconia, e.g., colloidal oramorphous zirconia, and mixtures of any of the foregoing; or aninorganic oxide of one type upon which is deposited an organic oxide ofanother type.

Non-polymeric, inorganic materials useful in forming the particles usedin the present invention can comprise inorganic materials selected fromgraphite, metals, oxides, carbides, nitrides, borides, sulfides,silicates, carbonates, sulfates, and hydroxides. A non-limiting exampleof a useful inorganic oxide is zinc oxide. Non-limiting examples ofsuitable inorganic sulfides include molybdenum disulfide, tantalumdisulfide, tungsten disulfide, and zinc sulfide. Non-limiting examplesof useful inorganic silicates include aluminum silicates and magnesiumsilicates, such as vermiculite. Non-limiting examples of suitable metalsinclude molybdenum, platinum, palladium, nickel, aluminum, copper, gold,iron, silver, alloys, and mixtures of any of the foregoing.

In certain embodiments, the particles can be selected from fumed silica,amorphous silica, colloidal silica, alumina, colloidal alumina, titaniumdioxide, iron oxide, cesium oxide, yttrium oxide, colloidal yttria,zirconia, colloidal zirconia, and mixtures of any of the foregoing. Incertain embodiments, the particles comprise colloidal silica. Asdisclosed above, these materials can be surface treated or untreated.Other useful particles include surface-modified silicas, such as aredescribed in U.S. Pat. No. 5,853,809 at column 6, line 51 to column 8,line 43, incorporated herein by reference.

As another alternative, a particle can be formed from a primary materialthat is coated, clad or encapsulated with one or more secondarymaterials to form a composite material that has a harder surface.Alternatively, a particle can be formed from a primary material that iscoated, clad or encapsulated with a differing form of the primarymaterial to form a composite material that has a harder surface.

In one example, and without limiting the present invention, an inorganicparticle formed from an inorganic material, such as silicon carbide oraluminum nitride, can be provided with a silica, carbonate or nanoclaycoating to form a useful composite particle. In another non-limitingexample, a silane coupling agent with alkyl side chains can interactwith the surface of an inorganic particle formed from an inorganic oxideto provide a useful composite particle having a “softer” surface. Otherexamples include cladding, encapsulating or coating particles formedfrom non-polymeric or polymeric materials with differing non-polymericor polymeric materials. A specific non-limiting example of suchcomposite particles is DUALITE™, which is a synthetic polymeric particlecoated with calcium carbonate that is commercially available from Pierceand Stevens Corporation of Buffalo, N.Y.

In certain embodiments, the particles used in the present invention havea lamellar structure. Particles having a lamellar structure are composedof sheets or plates of atoms in hexagonal array, with strong bondingwithin the sheet and weak van der Waals bonding between sheets,providing low shear strength between sheets. A non-limiting example of alamellar structure is a hexagonal crystal structure. Inorganic solidparticles having a lamellar fullerene (i.e., buckyball) structure arealso useful in the present invention.

Non-limiting examples of suitable materials having a lamellar structureinclude boron nitride, graphite, metal dichalcogenides, mica, talc,gypsum, kaolinite, calcite, cadmium iodide, silver sulfide and mixturesthereof. Suitable metal dichalcogenides include molybdenum disulfide,molybdenum diselenide, tantalum disulfide, tantalum diselenide, tungstendisulfide, tungsten diselenide and mixtures thereof.

The particles can be formed from non-polymeric, organic materials.Non-limiting examples of non-polymeric, organic materials useful in thepresent invention include, but are not limited to, stearates (such aszinc stearate and aluminum stearate), diamond, carbon black andstearamide.

The particles used in the present invention can be formed from inorganicpolymeric materials. Non-limiting examples of useful inorganic polymericmaterials include polyphosphazenes, polysilanes, polysiloxanes,polygermanes, polymeric sulfur, polymeric selenium, silicones andmixtures of any of the foregoing. A specific, non-limiting example of aparticle formed from an inorganic polymeric material suitable for use inthe present invention is Tospearl, which is a particle formed fromcross-linked siloxanes and is commercially available from ToshibaSilicones Company, Ltd. of Japan.

The particles can be formed from synthetic, organic polymeric materials.Non-limiting examples of suitable organic polymeric materials include,but are not limited to, thermoset materials and thermoplastic materials.Non-limiting examples of suitable thermoplastic materials includethermoplastic polyesters, such as polyethylene terephthalate,polybutylene terephthalate and polyethylene naphthalate, polycarbonates,polyolefins, such as polyethylene, polypropylene and polyisobutene,acrylic polymers, such as copolymers of styrene and an acrylic acidmonomer and polymers containing methacrylate, polyamides, thermoplasticpolyurethanes, vinyl polymers, and mixtures of any of the foregoing.

Non-limiting examples of suitable thermoset materials include thermosetpolyesters, vinyl esters, epoxy materials, phenolics, aminoplasts,thermoset polyurethanes and mixtures of any of the foregoing. Aspecific, non-limiting example of a synthetic polymeric particle formedfrom an epoxy material is an epoxy microgel particle.

The particles can also be hollow particles formed from materialsselected from polymeric and non-polymeric inorganic materials, polymericand non-polymeric organic materials, composite materials and mixtures ofany of the foregoing. Non-limiting examples of suitable materials fromwhich the hollow particles can be formed are described above.

In certain embodiments, the particles used in the present inventioncomprise an organic pigment, for example, azo compounds (monoazo,di-azo, β-Naphthol, Naphthol AS salt type azo pigment lakes,benzimidazolone, di-azo condensation, isoindolinone, isoindoline), andpolycyclic (phthalocyanine, quinacridone, perylene, perinone,diketopyrrolo pyrrole, thioindigo, anthraquinone, indanthrone,anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine,triarylcarbonium, quinophthalone) pigments, and mixtures of any of theforegoing. In certain embodiments, the organic material is selected fromperylenes, quinacridones, phthalocyanines, isoindolines, dioxazines(that is, triphenedioxazines), 1,4-diketopyrrolopyrroles,anthrapyrimidines, anthanthrones, flavanthrones, indanthrones,perinones, pyranthrones, thioindigos,4,4′-diamino-1,1′-dianthraquinonyl, as well as substituted derivativesthereof, and mixtures thereof.

Perylene pigments used in the practice of the present invention may beunsubstituted or substituted. Substituted perylenes may be substitutedat imide nitrogen atoms for example, and substituents may include analkyl group of 1 to 10 carbon atoms, an alkoxy group of 1 to 10 carbonatoms and a halogen (such as chlorine) or combinations thereof.Substituted perylenes may contain more than one of any one substituent.The diimides and dianhydrides of perylene-3,4,9,10-tetracarboxylic acidare preferred. Crude perylenes can be prepared by methods known in theart.

Phthalocyanine pigments, especially metal phthalocyanines may be used.Although copper phthalocyanines are more readily available, othermetal-containing phthalocyanine pigments, such as those based on zinc,cobalt, iron, nickel, and other such metals, may also be used.Metal-free phthalocyanines are also suitable. Phthalocyanine pigmentsmay be unsubstituted or partially substituted, for example, with one ormore alkyl (having 1 to 10 carbon atoms), alkoxy (having 1 to 10 carbonatoms), halogens such as chlorine, or other substituents typical ofphthalocyanine pigments. Phthalocyanines may be prepared by any ofseveral methods known in the art. They are typically prepared by areaction of phthalic anhydride, phthalonitrile, or derivatives thereof,with a metal donor, a nitrogen donor (such as urea or the phthalonitrileitself), and an optional catalyst, preferably in an organic solvent.

Quinacridone pigments, as used herein, include unsubstituted orsubstituted quinacridones (for example, with one or more alkyl, alkoxy,halogens such as chlorine, or other substituents typical of quinacridonepigments), and are suitable for the practice of the present invention.The quinacridone pigments may be prepared by any of several methodsknown in the art but are preferably prepared by thermally ring-closingvarious 2,5-dianilinoterephthalic acid precursors in the presence ofpolyphosphoric acid.

Isoindoline pigments, which can optionally be substituted symmetricallyor unsymmetrically, are also suitable for the practice of the presentinvention can be prepared by methods known in the art. A suitableisoindoline pigment, Pigment Yellow 139, is a symmetrical adduct ofiminoisoindoline and barbituric acid precursors. Dioxazine pigments(that is, triphenedioxazines) are also suitable organic pigments and canbe prepared by methods known in the art.

Mixtures of any of the previously described inorganic particles and/ororganic particles can also be used.

If desired, the particles described above can be formed intonanoparticles. In certain embodiments, the nanoparticles are formed insitu during formation of an aqueous dispersion of polymer-enclosedparticles, as described in more detail below. In other embodiments,however, the nanoparticles are formed prior to their incorporation intosuch an aqueous dispersion. In these embodiments, the nanoparticles canbe formed by any of a number of various methods known in the art. Forexample, the nanoparticles can be prepared by pulverizing andclassifying the dry particulate material. For example, bulk pigmentssuch as any of the inorganic or organic pigments discussed above, can bemilled with milling media having a particle size of less than 0.5millimeters (mm), or less than 0.3 mm, or less than 0.1 mm. The pigmentparticles typically are milled to nanoparticle sizes in a high energymill in one or more solvents (either water, organic solvent, or amixture of the two), optionally in the presence of a polymeric grindvehicle. If necessary, a dispersant can be included, for example, (if inorganic solvent) SOLSPERSE® 32000 or 32500 available from LubrizolCorporation, or (if in water) SOLSPERSE® 27000, also available fromLubrizol Corporation. Other suitable methods for producing thenanoparticles include crystallization, precipitation, gas phasecondensation, and chemical attrition (i.e., partial dissolution).

In certain embodiments, the polymer-enclosed color-imparting particlespresent in the first powder coating composition and/or the second powdercoating composition are formed from an aqueous dispersion ofpolymer-enclosed color-imparting particles. As used herein, the term“dispersion” refers to a two-phase system in which one phase includesfinely divided particles distributed throughout a second phase, which isa continuous phase. The dispersions often are oil-in-water emulsions,wherein an aqueous medium provides the continuous phase of thedispersion in which the polymer-enclosed particles are suspended as theorganic phase.

As used herein, the term “aqueous”, “aqueous phase”, “aqueous medium,”and the like, refers to a medium that either consists exclusively ofwater or comprises predominantly water in combination with anothermaterial, such as, for example, an inert organic solvent. In certainembodiments, the amount of organic solvent present in the aqueousdispersions is less than 20 weight percent, such as less than 10 weightpercent, or, in some cases, less than 5 weight percent, or, in yet othercases, less than 2 weight percent, with the weight percents being basedon the total weight of the dispersion. Non-limiting examples of suitableorganic solvents are propylene glycol monobutyl ether, ethylene glycolmonohexyl ether, ethylene glycol monobutyl ether, n-butanol, benzylalcohol, and mineral spirits.

The polymer-enclosed color-imparting particles used in the presentinvention may comprise, for example, a polymer selected from acrylicpolymers, polyurethane polymers, polyester polymers, polyether polymers,silicon-based polymers, co-polymers thereof, and mixtures thereof. Suchpolymers can be produced by any suitable method known to those skilledin the art to which the present invention pertains. Suitable polymerinclude those disclosed in U.S. patent application Ser. No. 10/876,031at [0061] to [0076], the cited portion of which being incorporated byreference herein, and United States Patent Application Publication No.2005/0287348 A1 at [0042] to [0044], the cited portion of which beingincorporation by reference herein.

In certain embodiments, such aqueous dispersions comprisecolor-imparting particles enclosed by a friable polymer. As used herein,the term “friable polymer” refers to a polymer that is easily pulverizedat ambient conditions. That is, upon removal of liquid materials fromthe dispersion, the resulting solid material does not coalesce and iseasily broken into small fragments or pieces, such as would be suitableas a dry feed material to an extruder to produce a powder coatingcomposition. A film-forming polymer, on the other hand, would, uponremoval of liquid materials from the dispersion, form a self-supportingcontinuous film on at least a horizontal surface of a substrate. As usedherein, the term “ambient conditions” refers to refers to surroundingconditions, which is often around one atmosphere of pressure, 50%relative humidity, and 25° C.

In certain embodiments, the friable polymer comprises the reactionproduct of (i) a polymerizable polyester polyurethane, and (ii) anethylenically unsaturated monomer. As used herein, the term“polymerizable polyester polyurethane” refers to a polymer that includesa plurality of ester units,

and a plurality of urethane units,

has functional groups that are capable of being polymerized to form alarger polymer, and wherein R¹ is an alkyl, cycloalkyl or oxyalkylmoiety, R² is an alkyl or cycloalkyl moiety, and R³ is alkyl,cycloalkyl, arakyl, or aromatic moiety. In certain embodiments, thepolymerizable polyester polyurethane comprises a polyester polyurethanehaving terminal ethylenic unsaturation. As used herein, the phrase“terminal ethylenic unsaturation” means that at least some of theterminal ends of the polyester polyurethane contain a functional groupcontaining ethylenic unsaturation. Such polyester polyurethanes may alsoinclude, but need not necessarily include, internal ethylenicunsaturation. As a result, in certain embodiments, the aqueousdispersion comprises a polymerizable polyester polyurethane havingterminal ethylenic unsaturation which is prepared from reactantscomprising (a) a polyisocyanate, (b) a polyester polyol, and (c) amaterial comprising an ethylenically unsaturated group and an activehydrogen group. In certain embodiments, the polymerizable polyesterpolyurethane is formed from reactants further comprising (d) apolyamine, and/or (e) a material comprising an acid functional group oranhydride and a functional group reactive with isocyanate or hydroxylgroups. As used herein, the term “active-hydrogen group” refers tofunctional groups that are reactive with isocyanates as determined bythe Zerewitnoff test as described in the JOURNAL OF THE AMERICANCHEMICAL SOCIETY, Vol. 49, page 3181 (1927).

Polyisocyanates suitable for use in preparing the polymerizablepolyester polyurethane include aliphatical, cycloaliphatical,araliphatical, and/or aromatic isocyanates, and mixtures thereof.

Examples of useful aliphatic and cycloaliphatic polyisocyanates include4,4-methylenebisdicyclohexyl diisocyanate (hydrogenated MDI),hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),methylenebis(cyclohexyl isocyanate), trimethyl hexamethylenediisocyanate (TMDI), meta-tetramethylxylylene diisocyanate (TMXDI), andcyclohexylene diisocyanate (hydrogenated XDI). Other aliphaticpolyisocyanates include isocyanurates of IPDI and HDI.

Examples of suitable aromatic polyisocyanates include tolylenediisocyanate (TDI) (i.e., 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate or a mixture thereof), diphenylmethane-4,4-diisocyanate(MDI), naphthalene-1,5-diisocyanate (NDI), 3,3-dimethyl-4,4-biphenylenediisocyanate (TODI), crude TDI (i.e., a mixture of TDI and an oligomerthereof), polymethylenepolyphenyl polyisocyanate, crude MDI (i.e., amixture of MDI and an oligomer thereof), xylylene diisocyanate (XDI) andphenylene diisocyanate.

Polyisocyanate derivatives prepared from hexamethylene diisocyanate,1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (“IPDI”),including isocyanurates thereof, and/or4,4′-bis(isocyanatocyclohexyl)methane are suitable.

In certain embodiments, the amount of polyisocyanate used to prepare thepolymerizable polyester polyurethane ranges from 20 to 70 percent byweight, such as 30 to 60 percent by weight or, in some cases, 40 to 50percent by weight, with the weight percents being based on the totalweight of resin solids used to prepare the polymerizable polyesterpolyurethane.

Polyester polyols suitable for use in preparing the polymerizablepolyester polyurethane may be prepared by any suitable method, e.g.,using saturated dicarboxylic acids or anhydrides thereof (or combinationof acids and anhydrides) and polyhydric alcohols, or by ring opening ofcaprolactones, e.g., epsilon caprolactone. Such polyester polyols arecommercially available in various molecular weights. Aliphaticdicarboxylic acids suitable for preparing polyesters include thosecontaining from 4 to 14, such as 6 to 10, carbon atoms inclusive.Examples of such dicarboxylic acids include: succinic acid, glutaricacid, adipic acid, pimelic acid, suberic acid, azelaic aid and sebacicacid. Corresponding anhydrides can also be used. Typically, adipic andazelaic acids are used.

Polyhydric alcohols used in the preparation of polyester polyolssuitable for use in preparing the polymerizable polyester polyurethaneinclude, without limitation, aliphatic alcohols containing at least 2hydroxy groups, e.g., straight chain glycols containing from 2 to 15,such as 4 to 8, carbon atoms inclusive. In certain embodiments, theglycols contain hydroxyl groups in the terminal positions. Non-limitingexamples of such polyhydric alcohols include ethylene glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol, 1,3-propane diol,1,3-butane diol, 1,4-butane diol, 1,5-pentane diol, 2,2-dimethylpropanediol, 1,5-hexane diol, 1,7-heptane diol, 1,8-octane diol, 1,10-decanediol and mixtures of such polyhydric alcohols.

In certain embodiments, the polyester polyol is prepared by reacting adicarboxylic acid (or anhydride thereof) with a polyhydric alcohol inthe presence of an esterification catalyst, such as an organo tincatalyst. The amount of acid and alcohol used will vary and depend onthe molecular weight polyester desired. Hydroxy terminated polyestersare obtained by utilizing an excess of the alcohol, thereby to obtainlinear chains containing a preponderance of terminal hydroxyl groups.Examples of polyesters include: poly(1,4-butylene adipate),poly(1,4-butylene succinate), poly(1,4-butylene glutarate),poly(1,4-butylene pimelate), poly(1,4-butylene suberate),poly(1,4-butylene azelate), poly(1,4butylene sebacate) and poly(epsiloncaprolactone). In certain embodiments, the polyester polyol utilized inpreparing the friable, polymerizable polyester polyurethane has a weightaverage molecular weight from 500 to 3000, such as 500 to 2500, or, insome cases, 900 to about 1300.

In certain embodiments, the amount of polyester polyol used to preparethe polymerizable polyester polyurethane included in certain embodimentsof the present invention ranges from 10 to 60 percent by weight, such as20 to 50 percent by weight or, in some cases, 30 to 40 percent byweight, with the weight percents being based on the total weight ofresin solids used to prepare the polymerizable polyester polyurethane.

As indicated, the polymerizable polyester polyurethane present incertain embodiments of the present invention is formed from a materialcomprising an ethylenically unsaturated group and an active hydrogengroup. Suitable ethylenically unsaturated groups include, for example,acrylates, methacrylates, allyl carbamates, and allyl carbonates. Theacrylate and methacrylate functional groups may be represented by theformula, CH₂═C(R₁)C(O)O—, wherein R₁ is hydrogen or methyl. The allylcarbamates and carbonates may be represented by the formulae,CH₂═CH—CH₂—NH—C(O)O—, and CH₂═CH—CH₂—O—(O)O—, respectively.

In certain embodiments, the material comprising an ethylenicallyunsaturated group and an active hydrogen group utilized in preparing thepolymerizable polyester polyurethane comprises ahydroxyalkyl(meth)acrylate. Suitable hydroxyalkyl (meth)acrylatesinclude those having from 1 to 18 carbon atoms in the alkyl radical, thealkyl radical being substituted or unsubstituted. Specific non-limitingexamples of such materials include 2-hydroxyethyl(meth)acrylate,2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate,hexane-1,6-diol mono(meth)acrylate, 4-hydroxybutyl (meth)acrylate, andmixtures thereof. As used herein, the term “(meth)acrylate” is meant toinclude both acrylates and methacrylates.

In certain embodiments, the amount of the material comprising anethylenically unsaturated group and an active hydrogen group used toprepare the polymerizable polyester polyurethane ranges from 1 to 12percent by weight, such as 2 to 8 percent by weight or, in some cases, 4to 6 percent by weight, with the weight percents being based on thetotal weight of resin solids used to prepare the polymerizable polyesterpolyurethane.

As previously indicated, in certain embodiments, the polymerizablepolyester polyurethane is formed from a polyamine. Useful polyaminesinclude, but are not limited to, primary or secondary diamines orpolyamines in which the groups attached to the nitrogen atoms can besaturated or unsaturated, aliphatic, alicyclic, aromatic,aromatic-substituted-aliphatic, aliphatic-substituted-aromatic andheterocyclic. Exemplary suitable aliphatic and alicyclic diaminesinclude 1,2-ethylene diamine, 1,2-porphylene diamine, 1,8-octanediamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like.Exemplary suitable aromatic diamines include phenylene diamines and thetoluene diamines, for example, o-phenylene diamine and p-tolylenediamine. These and other suitable polyamines are described in detail inU.S. Pat. No. 4,046,729 at column 6, line 61 to column 7, line 26, thecited portion of which being incorporated herein by reference.

In certain embodiments, the amount of polyamine used to prepare thepolymerizable polyester polyurethane ranges from 0.5 to 5 percent byweight, such as 1 to 4 percent by weight or, in some cases, 2 to 3percent by weight, with the weight percents being based on the totalweight of resin solids used to prepare the polymerizable polyesterpolyurethane.

As previously indicated, in certain embodiments, the polymerizablepolyester polyurethane is formed from a material comprising an acidfunctional group or anhydride and a functional group reactive with theisocyanate or hydroxyl groups of other components from which thepolyurethane material is formed. Useful acid functional materialsinclude compounds having the structure:X—Y—Zwherein X is OH, SH, NH₂, or NHR, and R includes alkyl, aryl,cycloalkyl, substituted alkyl, substituted aryl, and substitutedcycloalkyl groups, and mixtures thereof; Y includes alkyl, aryl,cycloalkyl, substituted alkyl, substituted aryl, and substitutedcycloalkyl groups, and mixtures thereof; and Z includes OSO₃H, COOH,OPO₃H₂, SO₂OH, POOH, and PO₃H₂, and mixtures thereof.

Examples of suitable acid functional materials include hydroxypivalicacid, 3-hydroxy butyric acid, D,L-tropic acid, D,L hydroxy malonic acid,D,L-malic acid, citric acid, thioglycolic acid, glycolic acid, aminoacid, 12-hydroxy stearic acid, dimethylol propionic acid, mercaptopropionic acid, mercapto butyric acid, mercapto-succinic acid, andmixtures thereof.

Useful anhydrides include aliphatic, cycloaliphatic, olefinic,cycloolefinic and aromatic anhydrides. Substituted aliphatic andaromatic anhydrides also are useful provided the substituents do notadversely affect the reactivity of the anhydride or the properties ofthe resultant polyurethane. Examples of substituents include chloro,alkyl and alkoxy. Examples of anhydrides include succinic anhydride,methylsuccinic anhydride, dodecenyl succinic anhydride,octadecenylsuccinic anhydride, phthalic anhydride, tetrahydrophthalicanhydride, methyltetrahydrophthalic anhydride, hexahydrophthalicanhydride, alkyl hexahydrophthalic anhydrides such asmethylhexahydrophthalic anhydride, tetrachlorophthalic anhydride,endomethylene tetrahydrophthalic anhydride, trimellitic anhydride,chlorendic anhydride, itaconic anhydride, citraconic anhydride, maleicanhydride, and mixtures thereof.

In certain embodiments, the acid functional material or anhydrideprovides the polymerizable polyester polyurethane with anionic ionizablegroups which can be ionized for solubilizing the polymer in water. As aresult, in certain embodiments, the polymerizable polyester polyurethaneis water-dispersible. As used herein, the term “water-dispersible” meansthat a material may be dispersed in water without the aid or use of asurfactant. As used herein, the term “ionizable” means a group capableof becoming ionic, i.e., capable of dissociating into ions or becomingelectrically charged. An acid may be neutralized with base to from acarboxylate salt group. Examples of anionic groups include —OSO₃ ⁻,—COO⁻, —OPO₃ ⁼, —SO₂O, —POO⁻; and PO₃ ⁼.

In certain embodiments, the amount of the material comprising an acidfunctional group or anhydride and a functional group reactive withisocyanate or hydroxyl groups used to prepare the polymerizablepolyester polyurethane ranges from 5 to 20 percent by weight, such as 7to 15 percent by weight or, in some cases, 8 to 12 percent by weight,with the weight percents being based on the total weight of resin solidsused to prepare the polymerizable polyester polyurethane.

As indicated, in certain embodiments, the acid groups are neutralizedwith a base. Neutralization can range from 0.6 to 1.1, such as 0.4 to0.9, or, in some cases, 0.8 to 1.0, of the total theoreticalneutralization equivalent. Suitable neutralizing agents includeinorganic and organic bases such as sodium hydroxide, potassiumhydroxide, ammonia, amines, alcohol amines having at least one primary,secondary, or tertiary amino group and at least one hydroxyl group.Suitable amines include alkanolamines such as monoethanolamine,diethanolamine, dimethylaminoethanol, diisopropanolamine, and the like.

The polymerizable polyester polyurethane present in certain embodimentsof the present invention may be formed by combining the above-identifiedcomponents in any suitable arrangement. For example, the polymerizablepolyester polyurethane may be prepared by solution polymerizationtechniques understood by those skilled in the art to which the presentinvention pertains.

As should be apparent from the foregoing description, the polymerizablepolyester polyurethane can be nonionic, anionic or cationic. In certainembodiments, the polymerizable polyester polyurethane will have a weightaverage molecular weight of less than 150,000 grams per mole, such asfrom 10,000 to 100,000 grams per mole, or, in some cases, from 40,000 to80,000 grams per mole. The molecular weight of the polyurethane and anyother polymeric materials described herein is determined by gelpermeation chromatography using a polystyrene standard.

As previously indicated, in certain embodiments of the presentinvention, a friable polymer is present that comprises the reactionproduct of (i) a polymerizable polyester polyurethane, such as thatpreviously described, and (ii) an ethylenically unsaturated monomer.Suitable ethylenically unsaturated monomers include any of thepolymerizable ethylenically, unsaturated monomers, including vinylmonomers known in the art. Non-limiting examples of useful ethylenicallyunsaturated carboxylic acid functional group-containing monomers include(meth)acrylic acid, beta-carboxyethyl acrylate, acryloxypropionic acid,crotonic acid, fumaric acid, monoalkyl esters of fumaric acid, maleicacid, monoalkyl esters of maleic acid, itaconic acid, monoalkyl estersof itaconic acid and mixtures thereof. As used herein, “(meth)acrylic”and terms derived therefrom are intended to include both acrylic andmethacrylic.

Non-limiting examples of other useful ethylenically unsaturated monomersfree of carboxylic acid functional groups include alkyl esters of(meth)acrylic acids, for example, ethyl(meth)acrylate,methyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,2-hydroxyethyl(meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl(meth)acrylate, isobornyl(meth)acrylate, lauryl (meth)acrylate, andethylene glycol di(meth)acrylate; vinyl aromatics such as styrene andvinyl toluene; (meth)acrylamides such as N-butoxymethyl acrylamide;acrylonitriles; dialkyl esters of maleic and fumaric acids; vinyl andvinylidene halides; vinyl acetate; vinyl ethers; allyl ethers; allylalcohols; derivatives thereof and mixtures thereof.

The ethylenically unsaturated monomers also can include ethylenicallyunsaturated, beta-hydroxy ester functional monomers, such as thosederived from the reaction of an ethylenically unsaturated acidfunctional monomer, such as a monocarboxylic acid, for example, acrylicacid, and an epoxy compound which does not participate in the freeradical initiated polymerization with the unsaturated acid monomer.Examples of such epoxy compounds are glycidyl ethers and esters.Suitable glycidyl ethers include glycidyl ethers of alcohols and phenolssuch as butyl glycidyl ether, octyl glycidyl ether, phenyl glycidylether and the like.

In certain embodiments, the polymerizable polyester polyurethane and theethylenically unsaturated monomer are present in the aqueous dispersionin a weight ratio of 95:5 to 30:70, such as 90:10 to 40:60, or, in somecases, from 80:20 to 60:40.

The aqueous dispersions described herein can be prepared by any of avariety of methods. For example, in certain embodiments, the aqueousdispersion is prepared by a method comprising (A) providing a mixture,in an aqueous medium, of (i) color-imparting particles, (ii) one or morepolymerizable, ethylenically unsaturated monomers; and/or (iii) amixture of one or more polymerizable unsaturated monomers with one ormore polymers; and/or (iv) one or more polymers, and then subjecting themixture to high stress shear conditions in the presence of an aqueousmedium. Such methods are described in detail in U.S. patent applicationSer. No. 10/876,031 at [0054] to [0090], the cited portion of whichbeing incorporated by reference herein, and United States PatentApplication Publication No. 2005/0287348 A1 at [0036] to [0050], thecited portion of which being incorporation by reference herein.

In certain embodiments, however, the aqueous dispersions are made by amethod comprising (1) providing a mixture, in an aqueous medium, of (i)color-imparting particles, (ii) a polymerizable ethylenicallyunsaturated monomer, and (iii) a water-dispersible polymerizabledispersant, and (2) polymerizing the ethylenically unsaturated monomerand polymerizable dispersant to form polymer-enclosed color-impartingparticles comprising a water-dispersible polymer. In these embodiments,the polymerizable dispersant may comprise any polymerizable materialthat is water-dispersible and which, upon polymerization with theethylenically unsaturated monomer, produces polymer-enclosedcolor-imparting particles comprising a water-dispersible polymer, insome cases, a water-dispersible, friable polymer. In certainembodiments, the polymerizable dispersant comprises the previouslydescribed water-dispersible, polymerizable polyester polyurethane havingterminal ethylenic unsaturation.

In these embodiments, the water-dispersible polymerizable dispersant iscapable is dispersing itself and other materials, including theethylenically unsaturated monomers, in the aqueous medium without theneed for surfactants and/or high shear conditions. As a result, theforegoing method for making an aqueous dispersion of polymer-enclosedcolor-imparting particles is particularly suitable in situations whereuse of the high stress shear conditions described in U.S. patentapplication Ser. No. 10/876,031, at [0081] to [0084] and United StatesPatent Application Publication No. 2005/0287348 A1 at [0046] is notdesired or feasible. Therefore, in certain embodiments, the aqueousdispersion of polymer-enclosed color-imparting particles is prepared bya method that does not include the step of subjecting the mixture ofcolor-imparting particles, polymerizable ethylenically unsaturatedmonomer, and water-dispersible polymerizable dispersant to high stressshear conditions.

In addition, the foregoing method enables the formation of nanoparticlesin situ, rather than requiring their formation prior to the preparationof the aqueous dispersion. In these methods, particles having a primaryparticle size of 1 micron or more, after being mixed with theethylenically unsaturated monomer and the water-dispersiblepolymerizable dispersant in the aqueous medium, may be formed intocolor-imparting nanoparticles (i.e., the nanoparticles are formed insitu). In certain embodiments, the color-imparting nanoparticles areformed by subjecting the aqueous medium to pulverizing conditions. Forexample, the particles can be milled with milling media having aparticle size of less than 0.5 millimeters, or less than 0.3millimeters, or, in some cases, less than 0.1 millimeters. In theseembodiments, the color-imparting particles can be milled to nanoparticlesize in a high energy mill in the presence of the aqueous medium, thepolymerizable ethylenically unsaturated monomer, and thewater-dispersible polymerizable dispersant. If desired, anotherdispersant can be used, such as SOLSPERSE 27000, available from Avecia,Inc.

As indicated, the foregoing methods for making aqueous dispersions ofpolymer-enclosed color-imparting particles include the step ofpolymerizing the ethylenically unsaturated monomer and polymerizabledispersant to form polymer-enclosed color-imparting particles comprisinga water-dispersible polymer. In certain embodiments, at least a portionof the polymerization occurs during formation of nanoparticles, ifapplicable. Also, a free radical initiator may be used. Both water andoil soluble initiators can be used.

Non-limiting examples suitable water-soluble initiators include ammoniumperoxydisulfate, potassium peroxydisulfate and hydrogen peroxide.Non-limiting examples of oil soluble initiators include t-butylhydroperoxide, dilauryl peroxide and 2,2′-azobis(isobutyronitrile). Inmany cases, the reaction is carried out at a temperature ranging from20° to 80° C. The polymerization can be carried out in either a batch ora continuous process. The length of time necessary to carry out thepolymerization can range from, for example, 10 minutes to 6 hours,provided that the time is sufficient to form a polymer in situ from theone or more ethylenically unsaturated monomers.

Once the polymerization process is complete, the resultant product is astable dispersion of polymer-enclosed color-imparting particles in anaqueous medium which can contain some organic solvent. Some or all ofthe organic solvent can be removed via reduced pressure distillation ata temperature, for example, of less than 40° C. As used herein, the term“stable dispersion” or “stably dispersed” means that thepolymer-enclosed color-imparting particles neither settle nor coagulatenor flocculate from the aqueous medium upon standing.

In certain embodiments, the polymer-enclosed particles are present inthe aqueous dispersions in an amount of at least 10 weight percent, orin an amount of 10 to 80 weight percent, or in an amount of 25 to 50weight percent, or in an amount of 25 to 40 weight percent, with weightpercents being based on weight of total solids present in thedispersion.

In certain embodiments, the dispersed polymer-enclosed particles have amaximum haze of 10%, or, in some cases, a maximum haze of 5%, or, in yetother cases, a maximum haze of 1%, or, in other embodiments, a maximumhaze of 0.5%. As used herein, “haze” is determined by ASTM D1003.

The haze values for the polymer-enclosed particles described herein aredetermined by first having the particles, such as nanoparticles,dispersed in a liquid (such as water, organic solvent, and/or adispersant, as described herein) and then measuring these dispersionsdiluted in a solvent, for example, butyl acetate, using a Byk-GardnerTCS (The Color Sphere) instrument having a 500 micron cell path length.Because the % haze of a liquid sample is concentration dependent, the %haze as used herein is reported at a transmittance of about 15% to about20% at the wavelength of maximum absorbance. An acceptable haze may beachieved for relatively large particles when the difference inrefractive index between the particles and the surrounding medium islow. Conversely, for smaller particles, greater refractive indexdifferences between the particle and the surrounding medium may providean acceptable haze.

In certain embodiments, particularly wherein the polymer-enclosedparticles comprise a friable polymer, the aqueous dispersion ofpolymer-enclosed color-imparting particles may then be further processedby (1) removing water from the aqueous dispersion to form a solidmaterial comprising the polymer-enclosed color-imparting particles, and(2) fragmenting the solid material. In these embodiments, the water canbe removed from the aqueous dispersion by any suitable drying method,such as through the use of a drum dryer, a roller dryer, a spray dryer,or the like. Moreover, the solid material can be fragmented by anysuitable technique, such as through the use of a hammer mill or thelike. Following fragmentation, the resultant granules may be furtherprocessed, such as by being screened in a classifier, before packaging.

In the present invention, the polymer-enclosed color-imparting particlesare incorporated into a powder coating composition. In addition to thepolymer-enclosed particles, such powder coating compositions maycomprise a particulate film-forming resin. Suitable film-forming resinsinclude, for example, an epoxy resin, such as an epoxy group-containingacrylic polymer or a polyglycidyl ether of a polyhydric alcohol and asuitable curing agent for the epoxy resin, such as a polyfunctionalcarboxylic acid group-containing material or a dicyanamide. Examples ofcurable particulate resinous materials are described in U.S. Pat. No. RE32,261 and U.S. Pat. No. 4,804,581, incorporated by reference herein.Examples of other suitable particulate film-forming resins arecarboxylic acid functional resins, such as carboxylic acid functionalpolyesters and acrylic polymers and suitable curing agents for suchmaterials, such as triglycidyl isocyanurate and beta-hydroxyalkylamidecuring agents as described, for example, in U.S. Pat. No. 4,801,680 andU.S. Pat. No. 4,988,767, incorporated by reference herein.

In certain embodiments, such powder coating compositions comprise from50 to 90 percent by weight, such as 60 to 80 percent by weight, of theparticulate film-forming resin, based on the total weight of the powdercoating composition. In certain embodiments, such powder coatingcompositions comprise from 0.1 to 50 percent by weight, such as 1 to 20percent by weight, of polymer-enclosed particles, based on the totalweight of the powder coating composition.

These powder coating compositions can optionally include other materialssuch as other pigments, fillers, light stabilizers, flow modifiers,anti-popping agents, and anti-oxidants. Suitable pigments include, forexample, titanium dioxide, ultramarine blue, phthalocyanine blue,phthalocyanine green, carbon black, graphite fibrils, black iron oxide,chromium green oxide, ferride yellow and quindo red.

Anti-popping agents can be added to the composition to allow anyvolatile material to escape from the film during baking. Benzoin is acommonly preferred anti-popping agent and when used is generally presentin amounts of from 0.5 to 3.0 percent by weight based on total weight ofthe powder coating composition.

Such powder coating compositions may also include fumed silica or thelike to reduce caking of the powder during storage. An example of afumed silica is sold by Cabot Corporation under the trademark CAB-O-SIL.The fumed silica is present in amounts ranging from 0.1 to 1 percent byweight based on total weight of the powder coating formulation.

The polymer-enclosed color-imparting particles may be incorporated intothe powder coating composition by any of a variety of methods. Forexample, in embodiments wherein the polymer-enclosed particles comprisea friable polymer, the polymer-enclosed color-imparting particles andother coating components are all embodied in a dried, particulate form,blended together, and then melt blended in an extruder. In otherembodiments, however, such as those cases wherein an aqueous dispersionof polymer-enclosed particles is used that does not comprise a friablepolymer, the polymer-enclosed color-imparting particles are incorporatedinto the powder coating composition by a method comprising (1)introducing to an extruder powder coating composition componentscomprising: (a) an aqueous dispersion of polymer-enclosedcolor-imparting particles, and (b) dry materials; (2) blending (a) and(b) in the extruder; (3) devolatilizing the blend to form an extrudate;(4) cooling the extrudate, and (5) milling the extrudate to a desiredparticle size. As used herein, the term “devolatilizing” means to removevolatile materials, including water and organic solvents. In certainembodiments, such powder coating compositions are made by a methodand/or apparatus described in United States Patent ApplicationPublication Nos. 2005/0212159A1; 2005/0212171A1; and/or 2005/0213423A1,the relevant disclosures of which being incorporated herein byreference.

In the foregoing methods, the dry materials may include the particulatefilm-forming resin described earlier as well as any other compositionadditives. The dry materials may be first blending in a high shear mixersuch as a planetary mixture. In certain embodiments, the dry materialsand the aqueous dispersion of the present invention are then blended inan extruder at a temperature ranging from 80° C. to 150° C. Theextrudate is then cooled and pulverized into a particulate blend.

In accordance with the present invention, the powder coating compositioncomprising polymer-enclosed color-imparting particles is mixed withanother powder coating composition, which may, and often does, alsoinclude polymer-enclosed color-imparting particles, to form a powdercoating composition of the present invention. In addition to thepolymer-enclosed color-imparting particles, such powder coatingcompositions may comprise a particulate film-forming resin, such asthose described earlier. In certain embodiments, the film-forming resinpresent in the first powder coating composition is the same as, or atleast compatible with, the film-forming resin present in the secondcoating composition.

As indicated earlier, the mixture of the first powder coating with thesecond powder coating composition produces a powder coating compositionof the present invention that, upon direct application to at least aportion of a substrate and cure, produces a decorative and durablecoating having a homogeneous hue different from the hue of the powdercoating compositions from which it is formed. In other words, the powdercoating compositions of the present invention are capable of producing adecorative and durable coating having a homogeneous hue different fromthe first hue and the second hue. As used herein, the term “directapplication”, and the like, means that the powder coating compositionneed not be subject to the Extrusion Process prior to application. Asused herein, the term “homogeneous hue different from the first hue andthe second hue” means that the coating is recognized by a person ashaving a uniform hue that is different from the first hue and the secondhue when viewed with the naked eye at any distance from the coating,including distances of one foot or less. Stated differently, the coatingdoes not have a “salt and pepper” appearance wherein each of the firsthue and the second hue is distinguishable by visual examination with thenaked eye. As used herein, the term “hue” refers to the quality of acolor as determined by its dominant wavelength.

The powder coating compositions of the invention can be applied to avariety of substrates including metallic substrates, for example,aluminum and steel substrates. The powder coating compositions are oftenapplied by spraying, and in the case of a metal substrate, byelectrostatic spraying, or by the use of a fluidized bed. The powdercoating compositions of the present invention can be applied in a singlesweep or in several passes to provide a film having a thickness aftercure of from about 1 to 10 mils (25 to 250 micrometers), usually about 2to 4 mils (50 to 100 micrometers). In many cases, after application ofthe powder coating composition, the coated substrate is heated to atemperature sufficient to cure the coating, often to a temperatureranging from 250° F. to 500° F. (121.1° C. to 260.0° C.) for 1 to 60minutes, such as 300° F. to 400° F. (148.9° C. to 204.4° C.) for 15 to30 minutes.

As a result, the present invention is also directed to articles, such asmetal articles, at least partially coated by a decorative and durablecoating having a homogeneous hue. The decorative and durable coating isdeposited directly from a powder coating composition comprising amixture of a first powder coating composition having a first hue and asecond powder coating composition having a second hue different from thefirst hue, wherein the first powder coating composition and/or thesecond powder coating composition comprises polymer-enclosedcolor-imparting particles. In the articles of the present invention, thehomogeneous hue is different that the first hue and the second hue.

In certain embodiments, the decorative and durable coating having ahomogeneous hue is also a non-hiding coating. As used herein, the term“non-hiding coating” refers to a coating layer deposited upon asubstrate wherein the surface beneath the coating layer is visible tothe naked eye. In certain embodiments of the present invention, thesurface beneath the non-hiding coating layer is visible when thenon-hiding layer is applied at a dry film thickness of 0.5 to 5.0 mils(12.7 to 127 microns). One way to assess non-hiding is by measurement ofopacity. As used herein, “opacity” refers to the degree to which amaterial obscures a substrate.

“Percent opacity” refers herein to the ratio of the reflectance of a drycoating film over a black substrate of 5% or less reflectance, to thereflectance of the same coating film, equivalently applied and dried,over a substrate of 85% reflectance. The percent opacity of a drycoating film will depend on the dry film thickness of the coating andthe concentration of color-imparting particles. In certain embodimentsof the present invention, the color-imparting non-hiding coating layerhas a percent opacity of no more than 90 percent, such as no more than50 percent, at a dry film thickness of one (1) mil (about 25 microns).

The powder coating compositions of the present invention may be used toform a single decorative and durable coating, for example, a monocoat, abase coat in a two-layered system or both; or as one or more layers of amulti-layered system including a clear top coating composition, acolorant layer and/or a base coating composition, and/or a primer layer,including, for example, an electrodeposition primer and/or aprimer-surfacer layer.

The present invention is also directed to substrates at least partiallycoated with a multi-layer composite coating wherein at least one coatinglayer is deposited from a powder coating composition of the presentinvention. In certain embodiments, for example, the powder coatingcomposition of the present invention comprises the basecoat layer in amulti-layer composite coating comprising a basecoat and a topcoat. As aresult, in these embodiments, after application and curing of the powdercoating composition of the present invention, at least one topcoat layercan be applied to the basecoat layer. The topcoat can, for example, bedeposited from a powder coating composition, an organic solvent-basedcoating composition or a water-based coating composition, as is wellknown in the art. The film-forming composition of the topcoat can be anyof the compositions useful in coatings applications, including, forexample, a film-forming composition that comprises a resinous binderselected from acrylic polymers, polyesters, including alkyds, andpolyurethanes. The topcoat composition can be applied by anyconventional coating technique such as brushing, spraying, dipping orflowing, but they are most often applied by spraying. The usual spraytechniques and equipment for air spraying, airless spray andelectrostatic spraying in either manual or automatic methods can beused.

As should be apparent from the foregoing description, the presentinvention is also directed to methods for preparing a decorative anddurable coating having a homogeneous hue. These methods comprise: (a)providing a first powder coating composition having a first hue, (b)providing a second powder coating composition having a second huedifferent than the first hue, (c) mixing the first powder coatingcomposition and the second powder coating composition, and (d) directlyapplying the mixture to at least a portion of a substrate. In thesemethods, the first powder coating composition and/or the second powdercoating composition comprises polymer-enclosed color-impartingparticles.

In certain embodiments, the present invention is embodied in the form ofa kit. As used herein, the term “kit” refers to a collection of articlesusable together. In these embodiments, the present invention is directedto a kit comprising: (a) a first container comprising a powder coatingcomposition having a first hue, and (b) a second container comprising apowder coating composition having a second hue different from the firsthue. In the kits of the present invention, the first container and/orthe second container comprises a powder coating composition comprisingpolymer-enclosed color-imparting particles, and upon mixture of thecontents of the first container with the contents of the secondcontainer, a powder coating composition is formed that, upon directapplication to at least a portion of a substrate and cure, produces adecorative and durable coating having a homogeneous hue different fromthe first hue and the second hue.

In addition, in certain embodiments, the present invention is directedto a method for producing a coating of a selected hue, i.e., colormatching, from a mixture of two or more powder coating compositions.These methods comprise: (a) providing a first powder coating compositionhaving a first hue, (b) providing a second powder coating compositionhaving a second hue different than the first hue, (c) mixing the firstpowder coating composition and the second powder coating composition ina proportion that results in a coating having the selected hue when themixture is directly applied to at least a portion of a substrate andcured. In these methods, the first powder coating composition and/or thesecond powder coating composition comprises polymer-enclosedcolor-imparting particles.

Illustrating the invention are the following examples that are not to beconsidered as limiting the invention to their details. All parts andpercentages in the examples, as well as throughout the specification,are by weight unless otherwise indicated.

EXAMPLES Example 1 Polyurethane Dispersion

This example describes the preparation of a polyurethane dispersion thatwas subsequently used to the form the respectivepolyurethane/nanopigment dispersions of Examples 2 to 3. Thepolyurethane dispersion was prepared from the following mixture ofingredients in the ratios indicated:

Ingredients Weight (grams) Charge I Poly (butylene oxide)¹ 355.6Dimethyloipropionic acid (DMPA) 119.2 Tri-ethylamine 54.0 Butylatedhydroxytoluene 2.2 Triphenyl phosphite 1.1 Charge II Hydroxyethylmethacrylate (HEMA) 27.8 Butyl methacrylate 48.4 Butyl acrylate 319.2Charge III Methylene bis(4-cyclohexylisocyanate) 558.9 Charge IV Butylmethacrylate 55.6 Charge V Deionized water 2086.3 Diethanolamine 20.2Ethylenediamine 26.9 Dimethylethanolamine 19.7 Charge VI Butylmethacrylate 50.0 ¹Poly (butylene oxide) having a number averagemolecular weight of 1000.

The polyurethane dispersion was prepared in a four neck round bottomflask equipped with an electronic temperature probe, mechanical stirrer,condenser, and a heating mantle. Charge I was stirred 5 minutes in theflask at a temperature of 125° C. Charge II was added and the mixturewas cooled to 70° C. Charge III was added over a 10 minute period.Charge IV was added and the resulting mixture was gradually heated to90° C. over 90 minutes and then held at 90° C. for 1 hour. Charge V wasstirred in a separate flask and heated to 60° C. 1387.8 g of thereaction product of Charges I, II, III, and IV was added to Charge Vover 10 minutes. Charge VI was added and the resulting mixture wascooled to room temperature. The final product was a translucent emulsionwith an acid value of 12.5, a Brookfield viscosity of 3710 centipoise(spindle #5 at 60 rpm), a pH of 7.6, and a nonvolatile content of 29.4%as measured at 110° C. for one hour.

Example 2 Polyurethane/Nanopigment Dispersion

This example describes the preparation of a nano-sized PB 15:3phthalocyanine blue pigment dispersion. The dispersion was prepared fromthe following mixture of ingredients in the ratios indicated:

Ingredients Weight (grams) Charge I Polyurethane dispersion of Example 17271.0 Deionized water 3293.1 Hydroquinone methyl ether (MEHQ) 2.0 PB15:3 pigment² 1079.5 Shellsol OMS (Shell Chemical Co.) 131.5 Charge IIDeionized water 102.4 t-Butyl hydroperoxide (70% aqueous solution) 12.3Charge III Deionized water 512.1 Ferrous ammonium sulfate 0.15 Sodiummetabisulfite 12.3 ²Commercially available from BASF Corp.

The ingredients were mixed using a Ross rotor/stator mixer Model#HSM-100L for 2.5 hours and then recycled through an Advantis V15 Draismill containing 500 ml of 0.3 mm Zirconox YTZ® grinding media in a oneliter grinding chamber. The mixture was milled at 1400 rpm for a totaltime of 19.0 hours. The progress of the milling was monitored byvisually observing changes in the transparency of thin films of samplesdrawn down over black and white Leneta paper. Charge II was added andthe resulting mixture was stirred 5 minutes at 11° C. Charge III wasadded in two aliquots over 5 minutes. The temperature of the mixtureincreased to 13° C. The final product was a blue liquid with aBrookfield viscosity of 26 centipoise (spindle #1 at 60 rpm), a pH of7.2, and a nonvolatile content of 30.0% as measured at 110° C. for onehour.

Example 3 Polyurethane/Nanopigment Dispersion

This example describes the preparation of a nano-sized PY 128 di-azoyellow pigment dispersion. The dispersion was prepared from thefollowing mixture of ingredients in the ratios indicated:

Ingredients Weight (grams) Charge I Polyurethane dispersion of Example 17271.0 Deionized water 3293.1 Hydroquinone methyl ether (MEHQ) 2.0 PY128 pigment3 1079.5 Shelisol OMS (Shell Chemical Co.) 131.5 Charge IIDeionized water 102.4 t-Butyl hydroperoxide (70% aqueous solution) 12.3Charge III Deionized water 512.1 Ferrous ammonium sulfate 0.15 Sodiummetabisulfite 12.3 ²Commercially available from CIBA.

The ingredients were mixed using a Ross rotor/stator mixer Model#HSM-100L for 5.5 hours and then recycled through an Advantis V15 Draismill containing 500 ml of 0.3 mm Zirconox YTZ® grinding media in a oneliter grinding chamber. The mixture was milled at 1400 rpm for a totaltime of 23 hours. The progress of the milling was monitored by visuallyobserving changes in the transparency of thin films of samples drawndown over black and white Leneta paper. Charge II was added and theresulting mixture was stirred 5 minutes. Charge III was added in twoaliquots over 5 minutes. The final product was a yellow liquid with aBrookfield viscosity of 53 centipoise (spindle #1 at 60 rpm), a pH of7.3, and a nonvolatile content of 28.8% as measured at 110° C. for onehour.

Example 4 Preparation of Powder Coating Composition Intermediate

This example describes the preparation of a core formula of drymaterials used to make the powder coating compositions of Examples 5 and6. The core formula was prepared from the following ingredients in theratios indicated:

Component Ingredients Parts by Weight 1 Uralac P880 Resin⁴ 81.136 2Primid XL552⁵ 11.064 3 Resinflow PL 200A⁶ 1 4 Benzoin⁷ 0.7 5 Irganox1076⁸ 1.2 6 Flow Additive 1.3 7 Tinuvin 144⁹ 1 8 Tinuvin 900⁹ 2 9Transparent Zinc Oxide¹⁰ 0.5 10 Aluminum Oxide C¹¹ 0.01 ⁴Commerciallyavailable from DSM Resins ⁵Commercially available from EMS ⁶Commerciallyavailable from Estron Chemical ⁷Commercially available from GCA Chemical⁸Commercially available from Clariant ⁹Commercially available from CIBA¹⁰Commercially available from Bayer Chemical ¹¹Commercial available fromPalmer Supplies

Components 1 to 9 were premixed in a Henschel Blender for 1 minute at1000 RPM. The mixture was then extruded through a Coperion W&P 30 mmco-rotating twin screw extruder at a 340 RPM screw speed and an averagetorque of 30-40%. The extruder was equipped with a low pressureinjection system and five independently temperature controlled zones, asdescribed in United States Published Patent Applications 2005/0213423;2005/0212159A1; and 2005/0212171A1. The five independently temperaturecontrolled zones were controlled at the following temperatures: Zone 1:60° C.; Zone 2: 120° C.; Zone 3: 130° C.; Zone 4: 120° C.; Zone 5: 100°C. The extrudate was cooled and ground in a mechanical milling system toa particle size of about 28 to 30 microns. Oversized particles wereremoved and component 10 was added.

Example 5 Preparation of Powder Coating Composition

A powder coating composition was prepared from the following ingredientsin the ratios indicated:

Component Ingredients Parts by Weight 1 Uralac P880 Resin 78.9 2 PrimidXL552 10.73 3 Resinflow PL 200A 0.97 4 Benzoin 0.68 5 Irganox 1076 1.166 Flow Additive 1.26 7 Tinuvin 144 0.97 8 Tinuvin 900 1.94 9 TransparentZinc Oxide 0.49 10 PB 15:3 pigment 3 11 Aluminum Oxide C 0.01

Components 1 to 10 were premixed in a Henschel Blender for 1 minute at1000 RPM. The mixture was then extruded through a Coperion W&P 30 mmco-rotating twin screw extruder at a 340 RPM screw speed and an averagetorque of 30-40%. The extruder was equipped with a low pressureinjection system and five independently temperature controlled zones, asdescribed in United States Published Patent Applications 2005/0213423;2005/0212159A1; and 2005/0212171A1. The five independently temperaturecontrolled zones were controlled at the following temperatures: Zone 1:60° C.; Zone 2: 120° C.; Zone 3: 130° C.; Zone 4: 120° C.; Zone 5: 100°C. The extrudate was cooled and ground in a mechanical milling system toa particle size of about 28 to 30 microns. Oversized particles wereremoved and component 10 was added.

Example 6 Preparation of Powder Coating Composition

A powder coating composition was prepared from the following ingredientsin the ratios indicated and using the procedure and apparatus describedin Example 5:

Component Ingredients Parts by Weight 1 Uralac P880 Resin 78.9 2 PrimidXL552 10.73 3 Resinflow PL 200A 0.97 4 Benzoin 0.68 5 Irganox 1076 1.166 Flow Additive 1.26 7 Tinuvin 144 0.97 8 Tinuvin 900 1.94 9 TransparentZinc Oxide 0.49 10 PY 128 pigment 3 11 Aluminum Oxide C 0.01

Example 7 Preparation of Powder Coating Composition

A powder coating composition was prepared from the powder coatingcomposition intermediate of Example 4 and the Polyurethane/NanopigmentDispersion of Example 2. The powder coating composition was preparedusing the Coperion W&P 30 mm co-rotating twin screw extruder andconditions described in Example 4 equipped with a low pressure injectionsystem and five independently temperature controlled zones, as describedin United States Published Patent Applications 2005/0213423;2005/0212159A1; and 2005/0212171A1. The powder coating compositionintermediate of Example 4 was fed to the extruder at a rate of 280 gramsper minute and the pigments dispersions were fed to the extruder at arate of 105 grams per minute through a low pressure injection system.Zone 4 was equipped with a devolatilization port for volatile vaporremoval. The extrudate was cooled and ground in a mechanical millingsystem to a particle size of about 28 to 30 microns.

Example 8 Preparation of Powder Coating Composition

A powder coating composition was prepared from the powder coatingcomposition intermediate of Example 4 and the Polyurethane/NanopigmentDispersion of Example 3 using the same apparatus and process conditionsdescribed in Example 7.

Example 9 Test Substrates

For Example 9a, a 50/50 weight percent combination of the powder coatingcompositions of Examples 5 and 6 were dry blended in a suitablecontainer by vigorous shaking. The resulting powder coating compositionwas electrostatically applied to 4″×12″ electrocoated panels. The panelswere cured at an appropriate elevated temperature and cooled to ambienttemperature. Upon close inspection of the resultant coating at adistance of less than 1 foot, the coating had a “salt and pepper”appearance in which the yellow and blue hue were individually visible.

For Example 9a, a 50/50 weight percent combination of the powder coatingcompositions of Examples 7 and 8 were dry blended in a suitablecontainer by vigorous shaking. The resulting powder coating compositionwas electrostatically applied to 4″×12″ electrocoated panels. The panelswere cured at an appropriate elevated temperature and cooled to ambienttemperature. Upon close inspection of the resultant coating at adistance of less than 1 foot, the coating had a homogeneous green hue.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications which are within the spirit and scopeof the invention, as defined by the appended claims.

1. A method for preparing a decorative and durable coating having ahomogeneous hue comprising: (a) dry-blend mixing a first powder coatingcomposition having a first hue and a second powder coating compositionhaving a second hue different than the first hue to form a heterogeneousassociation of the first powder coating composition and the secondpowder coating composition; and (b) directly applying the heterogeneousassociation of the first powder coating composition and the secondpowder coating composition to at least a portion of a substrate, whereinthe first powder coating composition and/or the second powder coatingcomposition comprises a particulate film-forming resin andpolymer-enclosed color-imparting nanoparticles, the color-impartingnanoparticles having average particle size of 300 nanometers or less,wherein the particulate film-forming resin comprises an epoxy functionalresin, wherein the polymer-enclosed color-imparting nanoparticles areenclosed by a polymer different from the particulate film-forming resin,wherein the polymer-enclosed color-imparting nanoparticles comprise apolymer comprising the reaction product of (i) an ethylenicallyunsaturated water-dispersible polymerizable dispersant, and (ii) anethylenically unsaturated monomer, and wherein the water-dispersiblepolymerizable dispersant comprises a polymer selected from the groupconsisting of polyurethane polymers, polyester polymers, polyetherpolymers, silicon-based polymers, co-polymers thereof, and mixturesthereof.
 2. The method of claim 1, wherein the first powder coatingcomposition and the second powder coating composition are both anextrusion product of an extruder feed comprising both the particulatefilm-forming resin and the polymer-enclosed color-impartingnanoparticles.
 3. The method of claim 2, wherein the extruder feedcomprises an aqueous dispersion of the polymer-enclosed color-impartingnanoparticles.
 4. The method of claim 2, wherein the first powdercoating composition and the second powder coating composition comprisethe same particulate film-forming resin.
 5. The method of claim 1,wherein the polymer-enclosed color-imparting nanoparticles comprisenanoparticles having an average particle size of 100 nanometers or less.6. The method of claim 1, wherein the nanoparticles comprise organicnanoparticles.
 7. The method of claim 1, wherein the polymer-enclosedcolor-imparting nanoparticles comprise a polymer comprising afree-radical polymerization reaction product of (i) the ethylenicallyunsaturated polymerizable polyester polyurethane, and (ii) theethylenically unsaturated monomer.
 8. The method of claim 7, wherein thepolymerizable polyester polyurethane comprises a polyester polyurethanehaving terminal ethylenic unsaturation.
 9. The method of claim 8,wherein the polyester polyurethane having terminal ethylenicunsaturation is prepared from reactants comprising: (a) apolyisocyanate; (b) a polyester polyol; and (c) a material comprising anethylenically unsaturated group and an active hydrogen group.
 10. Themethod of claim 1, wherein the coating is a non-hiding coating.
 11. Themethod of claim 1, wherein the particulate film-forming resin comprisesa carboxylic acid functional resin.
 12. A method for color matchingusing a powder coating composition comprising dry-blend mixing a firstpowder coating composition having a first hue and a second powdercoating composition having a second hue different than the first hue toform a heterogeneous association of the first powder coating compositionand the second powder coating composition in a proportion that resultsin a coating having a desired homogeneous hue when the heterogeneousassociation of the first powder coating composition and the secondpowder coating composition is directly applied to at least a portion ofa substrate and cured, wherein the first powder coating compositionand/or the second powder coating composition comprises a particulatefilm-forming resin and polymer-enclosed color-imparting nanoparticles,the color-imparting nanoparticles having average particle size of 300nanometers or less, wherein the particulate film-forming resin comprisesan epoxy functional resin, wherein the polymer-enclosed color-impartingnanoparticles are enclosed by a polymer different from the particulatefilm-forming resin, wherein the polymer-enclosed color-impartingnanoparticles comprise a polymer comprising the reaction product of (i)an ethylenically unsaturated water-dispersible polymerizable dispersant,and (ii) an ethylenically unsaturated monomer, and wherein thewater-dispersible polymerizable dispersant comprises a polymer selectedfrom the group consisting of polyurethane polymers, polyester polymers,polyether polymers, silicon-based polymers, co-polymers thereof, andmixtures thereof.
 13. The method of claim 12, wherein thepolymer-enclosed color-imparting nanoparticles comprise a polymercomprising a free-radical polymerization reaction product of (i) theethylenically unsaturated polymerizable polyester polyurethane, and (ii)the ethylenically unsaturated monomer.
 14. The method of claim 13,wherein the polymerizable polyester polyurethane comprises a polyesterpolyurethane having terminal ethylenic unsaturation.
 15. The method ofclaim 14, wherein the polyester polyurethane having terminal ethylenicunsaturation is prepared from reactants comprising: (a) apolyisocyanate; (b) a polyester polyol; and (c) a material comprising anethylenically unsaturated group and an active hydrogen group.
 16. Amethod for preparing a decorative and durable coating having ahomogeneous hue comprising: (a) dry-blend mixing a first powder coatingcomposition having a first hue and a second powder coating compositionhaving a second hue different than the first hue to form a heterogeneousassociation of the first powder coating composition and the secondpowder coating composition; and (b) directly applying the heterogeneousassociation of the first powder coating composition and the secondpowder coating composition to at least a portion of a substrate, whereinthe first powder coating composition and/or the second powder coatingcomposition comprises a particulate film-forming resin andcolor-imparting nanoparticles having average particle size of 300nanometers or less, wherein the particulate film-forming resin comprisesan epoxy functional resin, wherein the polymer-enclosed color-impartingnanoparticles are enclosed by an acrylic polymer different from theparticulate film-forming resin, wherein the first powder coatingcomposition and/or the second powder coating composition comprises 50 to90 percent by weight of a particulate film-forming resin comprising acarboxylic acid functional resin, wherein the polymer-enclosedcolor-imparting nanoparticles comprise a polymer comprising the reactionproduct of (i) an ethylenically unsaturated water-dispersiblepolymerizable dispersant, and (ii) an ethylenically unsaturated monomer,and wherein the water-dispersible polymerizable dispersant comprises apolymer selected from the group consisting of polyurethane polymers,polyester polymers, polyether polymers, silicon-based polymers,co-polymers thereof, and mixtures thereof.
 17. The method of claim 16,wherein the first powder coating composition and/or the second powdercoating composition comprises an extrusion product of an extruder feedcomprising both the particulate film-forming resin and thepolymer-enclosed color-imparting nanoparticles.
 18. The method of claim17, wherein the first powder coating composition and the second powdercoating composition are both the extrusion product of an extruder feedcomprising both the particulate film-forming resin and thepolymer-enclosed color-imparting nanoparticles.
 19. The method of claim17, wherein the extruder feed comprises an aqueous dispersion of thepolymer-enclosed color-imparting nanoparticles.
 20. The method of claim16, wherein the nanoparticles comprise organic nanoparticles.
 21. Themethod of claim 16, wherein the coating is a non-hiding coating.
 22. Themethod of claim 16, wherein the polymer-enclosed color-impartingnanoparticles comprise a polymer comprising a free-radicalpolymerization reaction product of (i) the ethylenically unsaturatedpolymerizable polyester polyurethane, and (ii) the ethylenicallyunsaturated monomer.
 23. The method of claim 22, wherein thepolymerizable polyester polyurethane comprises a polyester polyurethanehaving terminal ethylenic unsaturation.
 24. The method of claim 23,wherein the polyester polyurethane having terminal ethylenicunsaturation is prepared from reactants comprising: (a) apolyisocyanate; (b) a polyester polyol; and (c) a material comprising anethylenically unsaturated group and an active hydrogen group.